Several devices for utilizing the rise and fall of the tides or wave action to impart motion to mechanical systems are well known in the prior art. For example, such devices are the subjects of U.S. Pat. Nos. 378,452; 603,314; 1,036,502; 1,455,718; 1,623,341; 2,484,183; 3,268,154; 3,690,790; 3,697,764; and 3,925,986; and of the present applicant's pending U.S. patent application, Ser. No. 781,949, filed Mar. 28, 1977. The last of such listed patents contains a summary description of several of the earlier listed patents and is a particularly useful background reference. Of the aforementioned patents, those not summarized in U.S. Pat. No. 3,925,986 are summarized in the aforementioned pending application, Ser. No. 781,949. This pending application describes an apparatus for extracting power from the tides, the apparatus having a housing mounted on the ocean bed with ports of ingress and egress near the bottom or lower part of the housing, through which tidal waters may flow, valves for permitting low pressure air to be built up in the housing by tides and partial vacuum conditions in response to falling tides, and valving connecting this first housing to a second housing which is divided into two fluid communicating chambers. A float is disposed in each chamber and a rod attached to each of said floats extends through the second housing at a fluid-sealed aperture. The valving controls changes in the atmosphere pressure in the air above the fluid in each of the two chambers of the second housing, causing the floats and float rods to reciprocate and thereby provide usable mechanical output. The reciprocating action is a result of there being a fixed volume of liquid within the second housing, the specific portion of such liquid disposed within each chamber at any instant of time being a function of the relative atmospheric pressures present within the chambers.
Neither the aforementioned patent application nor any of the above-listed patents discloses or suggests the use of a water level differential which may be developed across a dam to provide a pressurized water flow for moving a constant volume of air between two chambers in reciprocating fashion, as in the present invention; likewise, they do not show that such reciprocating volume of air may be used to reciprocate a piston and piston rod to provide mechanically usable power in the manner of this invention. Nor is the use of a flexible, thin-walled material suggested by any of such art as suitable for the principal element of the required dam.